Stocks posted strong gains for a second day on Thursday, but Dell (NASDAQ: DELL) threatened to undo the rally after the close when the company posted disappointing quarterly results.

Dell's 11 percent sales growth to $16.4 billion was nearly $500 million above estimates, but the company's earnings of 33 cents a share were three cents below forecasts, as the company was hit by restructuring and investment costs and a move into lower-margin businesses like retail.

But the company's comments that economic weakness may be spreading drew the most attention. "The company sees continued conservatism in IT spending in the U.S., which has extended into Western Europe and several countries in Asia," the company said in its earnings press release.

Notebook sales were particularly strong, up 26%, but the results were a disappointment after the company's stellar April quarter, and its shares fell 10% in after-hours trading.

Stocks posted strong gains during the day after the U.S. Commerce Department said second-quarter growth was much strong than initially reported, up 3.3%. The rally was once again led by financial stocks.

On the Nasdaq's most active list, PMC-Sierra (NASDAQ: PMCS) and Level 3 (NASDAQ: LVLT) gained more than 5% each, and Sun (NASDAQ: JAVA), Juniper (NASDAQ: JNPR) and Symantec (NASDAQ: SYMC) rose nearly 3%. Juniper benefited from a positive article in Investor's Business Daily.

EMC (NYSE: EMC) and VMware (NYSE: VMW) posted 3% gains on the NYSE.

Stocks left out of the rally included Dell, Apple (NASDAQ: AAPL), Research in Motion (NASDAQ: RIMM), Qualcomm (NASDAQ: QCOM) and Nvidia (NASDAQ: NVDA). Apple was hit by iPhone security woes, the company's latest glitch.

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The Nasdaq rose 29 to 2411, the S&P gained 19 to 1300, and the Dow soared 212 to 11,715. Volume rose to 3.79 billion shares on the NYSE, and 1.62 billion on the Nasdaq. Advancers led by a 25-6 margin on the NYSE, and 21-7 on the Nasdaq. Upside volume was 82% on the NYSE, and 82% on the Nasdaq. New highs-new lows were 35-45 on the NYSE, and 60-81 on the Nasdaq.